The invention relates to a sheet-fed rotary printing machine for multicolor printing.
For the printing of small-format printing sheets it is a known practice to use printing units in which the cylinders participating in the printing, such as a plate cylinder, a rubber cylinder and a printing cylinder, have different diameters. Thereby mechanical expenditure can be saved in the field of the printing plates, of the rubber blankets or of the printing cylinder.
From DE-PS 24 35 203 there is known a sheet-fed rotary printing machine. It has, in the most diverse configurations, a plate cylinder with single or simple diameter, a rubber cylinder with multiple diameter and a printing cylinder with single diameter. Thereby from differently usable printing units from a particular plate cylinder a partial image of a print image can be printed on one of several segments of the rubber cylinder. Simultaneously this print image can be printed on a printing sheet guided on the printing cylinder, in which process the printing sheet with the printing cylinder revolves in correspondence to the movement of the segments of the rubber cylinder and is printed from this latter.
In U.S. Pat. No. 3,347,160 there is described an ink roller device for a multicolor rotary offset printing machine. This printing machine has a plate cylinder and a rubber cylinder in each case with multiple diameter to which there is allocated a printing cylinder with simple diameter. In the printing process the printing plate consisting of several image parts is generated on the plate cylinder from several cycled inking and moistening units, transferred to the multiply large rubber cylinder, and printed on a printing sheet guided on the printing cylinder. There the printing cylinder rotates a number of times corresponding to the diameter ratio between rubber cylinder and printing cylinder, until all the print image parts have been transferred onto the printing sheet. This multicolor printing machine is suited for the so-called proof printing.
What is disadvantageous in these devices is that even though they can be produced, to be sure, as individual printing units, the expenditure for the printing with images that contain more ink than the particular printing machine permits is very high. These printing machines, therefore, are suited only for special printing processes.
An object of the invention is to present a machine configuration which, with the simplest construction, has arbitrarily combinable printing mechanisms for the generating of prints with a different number of colors, renders unnecessary any changing of assemblies and is suited for high throughput with arbitrary edition levels.
Another object of the invention is to improve a device of the foregoing type, so that from standard elements there results a simple and therewith cheap printing machine which, by combining components of this type with one another, allow differently configurable multicolor printings, without it being necessary for the printing machine to be re-outfitted or to have too low a performance.
The present invention provides these and other advantages and overcomes the drawbacks of the prior art by providing a sheet-fed printing machine for printing sheets in a plurality of colors in which all the plate cylinders are provided with two printing plates and that in all the sheet conducting cylinders or drums there is only one gripper arrangement in operation. Here it is especially advantageous that, on the basis of standard printing machines, simplified forms of execution of printing machines are produced which with little expenditure permit economical printing processes, in which heed is given to a so-called xe2x80x9cslimxe2x80x9d or slender sheet running and the costs for building the machine are reduced because simple elements are used.
In the first place this can occur through the use of a printing cylinder with single diameter which rotates a number of times for the reception of the print images, while the other cylinders or drums provided with the same or with doubled diameter rotate only at half the speed of the printing cylinder.
In a further form of execution the rubber cylinder is constructed as a cylinder provided with single diameter. In standard printing processes proposed for this, it collects the prescribed print images of different colors on the plate cylinder and prints them in a single printing operation onto the printing sheets held on the printing cylinder.
These and other features and advantages of the invention will be more readily apparent upon reading the following description of preferred exemplary embodiments of the invention and upon reference to the drawings wherein: